This invention relates to a universal joint that is formed from a first joint yoke and a second joint yoke, each having a base portion that is centered on a longitudinal axis of rotation. From this base portion, two yoke arms extend that are attached to the base portion, are offset in opposite directions from the longitudinal axis, and end in respective free ends. Each yoke arm has an inner face that faces toward the longitudinal axis. Facing away from the inner face, each of the yoke arms has an outer face.
In each of the yoke arms, a cylindrical bearing bore is provided that extends between the outer face and the inner face. The bearing bores of both of the yoke arms are arranged on a common axis that intersects the longitudinal axis at a right angle. In the inner faces of both of the yoke arms, a recess is provided so that a step is formed in which a portion is provided that is open to the bearing bore. The two joint yokes are connected by a journal cross having four circular cylindrical trunnions that are arranged at right angles to each other. For each of the trunnions, a bearing bushing having a cylindrical envelope face and a cylindrical bore is provided. The bearing bushings are rotatably supported on each of the trunnions by interposed rolling members in form of rollers contained within the bearing bushings. The bearing bushings are, respectively, accommodated with their envelope face in the bearing bores of the yoke arms. By means of the opening, a support-free portion is achieved in which the bearing bushing is not supported by the mating yoke arm. Such a joint yoke is, for example, shown in the book “Gelenke and Gelenkwellen (“Joints and universal shafts”) by H.-Ch. Graf von Seherr-Thoss, F. Schmelz and E. Aucktor, second edition Springer Verlag, page 246, picture 5.5.
Such a closed embodiment of the yoke arms of a joint yoke for a universal joint has the advantage that it facilitates the assembly of a journal cross, as a space is provided by the opening through which the trunnion of a journal cross can be initially inserted into the mating bearing bore before the bearing bushing is mounted from the outside.
In universal joints for the transmission of high torques, i.e., a universal joint that has a corresponding large trunnion diameter and, therefore, corresponding large bearing bores in the yoke arms, it has been found that, for example, also in comparison to joint designs in which the yoke arms are separated, to be able to mount a journal cross, a distinctly worse bearing support is achieved so that the bearing life time is distinctly reduced. Decisive for this worsening is, in the closed joint yoke, the existence of the recess in the area of the free end of the yoke arms.
This invention is based on the object to propose a universal joint that, although a recess is provided enabling the insertion of a journal cross, is distinctly superior concerning bearing life time.